Re: [Plplot-devel] How do you specify special symbols and Greek letters with TrueType fonts?

[Alan W. I. <ir...@be...>]

On 2004-05-16 10:14-0700 Alan W. Irwin wrote:

> For the -dev png plots I am preparing for publication, I have been
> attempting to use the TrueType fonts that are available with the png device
> and the -drvopt text,smooth option.  Normal characters that are on the line,
> superscripted, or subscripted in either 2D and 3D plots seems to work. The
> only trouble I am having is with special symbols and Greek letters.

With private help from Andrew (Roach) I think my current publication needs
are taken care of with some clumsy, but effective workarounds.

On the dark side, there seems to be a current limitation that only the first
156 characters of any freetype font are accessible.  My own feeling is that
is unlikely to be a libfreetype issue since that library is heavily used by
a lot of users. But Andrew is having trouble finding any place in the PLplot
code where that limit is imposed. Off-hand does anybody know a place in our
code where decimal 100 is added to the font index then effectively
subtracted later? That would overflow an unsigned character and cause the
symptoms we are seeing.

On the bright side, I have been discovering a whole bunch of font options
PLplot -dev png -drvopt text,smooth,24bit users have access to.  For
example, there are the bluesky computer modern fonts postscript type 1
format.  We discussed those previously with regard to making nice-looking
documentation, but it turns out they are useful for our plots as well. Those
fonts appear in the /usr/share/texmf/fonts/type1/bluesky/ tree on my system,
and are in the Debian package called tetex-extra, and they work fine with
libfreetype (aside from the first 156 character issue). The only problem is
they are split between a large number of files and switching between font
files is currently rather clumsy because you have to set the
PLPLOT_SYMBOL_FONT environment variable each time.  (ToDo, use a modern font
configuration system such as Keith Packard's fontconfig that is available
with X and which serves as a user-friendly front-end for libfreetype.)
Anyhow, despite much sampling of fonts I haven't yet found the symbol and
Greek character font files I need yet in the bluesky tree.  I know the
symbols I need must be somewhere there since computer modern fonts are
extraordinarily comprehensive and satisfy almost all Math needs.  Perhaps
what I need is hidden from me by the current limit of the first 156
characters.

Another possibility that is accessible using libfreetype is truetype (as
opposed to the bluesky postscript type 1) computer modern fonts. I got these
from http://www.mozilla.org/projects/mathml/fonts/bakoma/texcm-ttf.zip. as
recommended by http://www.mozilla.org/projects/mathml/fonts/. They are
licensed for free distribution (see
http://www.mozilla.org/projects/mathml/fonts/bakoma/license.txt) so long as
you don't redistribute them for money yourself.

Anyhow, they seem better organized (from the perspective of our current
method of accessing fonts using PLPLOT_SYMBOL_FONT), and with fewer blank
characters in the first 156. So the cmsy10.ttf file, for example has a
gradient symbol while the corresponding bluesky
/usr/share/texmf/fonts/type1/bluesky/cm/cmsy10.pfb font file seems to have a
blank in the same location. I have yet to find a freely accessible font file
with Greek characters in the first 156 locations, but for my immediate
publication needs Andrew has given me such a font file privately that does
that.  So I can work around all the current freetype problems for my next
two publications, and therefore my immediate needs are taken care of.

To summarize my recent experience, Hershey fonts are not acceptable for the
png device because they look pretty awful for that inherently low-resolution
device (typically 800x600 pixels).  So that is why libfreetype support for
-dev png is so important. My recent experience with that shows there is
tremendous potential there for -dev png users (and in fact users of any
device once the required simple code changes are made for each device
driver) since there are so many excellent free fonts that are available via
libfreetype.  Nevertheless, there is also scope for improvement in the way
the libfreetype fonts are organized for PLplot (see ToDo item above), and we
also have to find and fix the current 156 character limit bug.

Alan
__________________________
Alan W. Irwin
email: ir...@be...
phone: 250-727-2902

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the PLplot scientific plotting software
package (plplot.org), the Yorick front-end to PLplot (yplot.sf.net), the
Loads of Linux Links project (loll.sf.net), and the Linux Brochure Project
(lbproject.sf.net).
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